CPAP treatment is a common ameliorative treatment for breathing disorders including OSA. CPAP treatment, as described in U.S. Pat. No. 4,944,310, provides pressurized air or other breathable gas to the entrance of a patient's airways at a pressure elevated above atmospheric pressure, typically in the range of 4-20 cm H2O. It is also known for the level of treatment pressure to vary during a period of treatment in accordance with patient need, that form of CPAP being known as automatically adjusting nasal CPAP treatment, as described in U.S. Pat. No. 5,245,995.
NIPPV is another form of treatment for breathing disorders that can involve a relatively higher pressure of gas being provided in the patient mask during the inspiratory phase of respiration and a relatively lower pressure or atmospheric pressure being provided in the patient mask during the expiratory phase of respiration. In other NIPPV modes, the pressure can be made to vary in a complex manner throughout the respiratory cycle. For example, the pressure at the mask during inspiration or expiration can be varied through the period of treatment.
Typically, the ventilation assistance for CPAP or NIPPV treatment is delivered to the patient by way of a nasal mask. Alternatively, a mouth mask full-face mask or nasal prongs can be used.
In this specification, any reference to CPAP treatment is to be understood as embracing all of the above-described forms of ventilation treatment or assistance.
A CPAP apparatus broadly includes a flow generator for supplying a continuous source of pressurized air or other breathable gas. Such a flow generator is typically a stand-alone unit having an electric motor driving a blower and is typically controlled by a servo-controller under the control of a microcontroller unit. Alternatively, other supplies of pressurized gas can be used. The flow generator is connected to the mask by a gas supply conduit or tube to supply the pressurized gas to an interior of the mask. The mask or gas supply conduit generally includes a venting system to vent exhalation gases from the interior of the mask to the atmosphere. The mask is normally secured to the wearer's head by a headgear or straps. The straps are adjusted with sufficient tension to achieve a gas-tight seal between the mask and the wearer's face. The mask generally includes a forehead support to rest against the user's forehead to support and stabilize the mask with respect to the user's face and prevent the mask from exerting undue pressure on the user's nose when the straps are tensioned. Examples of nasal masks are shown in U.S. Pat. Nos. 4,782,832 and 5,243,971.
One problem that arises with the use of masks is that a single shape of mask must be utilized for a large variety of users having differently shaped and sized heads and facial regions. Therefore, it is desirable for the forehead support to be adjustable to alter an extension between a forehead contacting portion of the forehead support and the mask frame, thereby accommodating a variety of users with a single mask configuration, while maintaining a comfortable fit and gas-tight seal for each user. Additionally, an adjustable forehead support can be adjusted to position the gas supply conduit in a desired position with respect to the user, such as to prevent the gas supply conduit from contacting the wearer's forehead or face and causing discomfort to the user.
Adjustable forehead supports are known. See, for example, the adjustable forehead supports disclosed in U.S. Pat. No. 6,119,693 to Kwok et al. and PCT International Patent Application Publication No. WO 00/78384 to Kwok et al., both assigned to the assignee of the present application. Both references disclose effective, durable forehead support mechanisms. However, these mechanisms require several components that increase the expense of manufacturing such mechanisms and make the mechanisms more appropriate for masks that will be used over an extended period of time, generally 3-6 months. Such mechanisms are relatively costly to use with masks intended for single or short-term use.
There are circumstances where an inexpensive, disposable short-term use mask is appropriate. For instance, such a mask might be appropriate under CPAP testing conditions where the testing is expected to last only a few days or weeks. Such a mask might also be used for patients admitted to hospitals for short-term stays. Extended use masks require periodic disassembly, cleaning and disinfecting, and reassembly to maintain sanitary conditions. The use of a disposable mask can eliminate such mask maintenance during extended treatment. Instead of performing the mask maintenance at the periodic intervals, a user can just dispose the disposable mask at the proper intervals and use a new disposable mask. However, for it to be generally desirable to use a disposable mask in such extended term treatment, the cost of the mask must be sufficiently low so as to compare favorably economically with the overall cost of an extended use mask, including the cost of the extended use mask, as well as the time required and nuisance of the periodic maintenance of the extended use mask.
Thus, there is a need for an inexpensive short-term use mask for providing breathable gases to a patient, as during CPAP treatment. To accommodate a large variety of users comfortably with a single mask configuration and maintain a gas-tight seal for each user, the mask should include a simple, easy to use adjustable forehead support mechanism. The mask should be inexpensive enough to be disposable during extended term CPAP treatment while comparing favorably economically to the use of an extended term mask. The mask should also be inexpensive enough to justify single-use. It is an object of the present invention to provide such a mask.